Position monitoring systems have been employed in mobile machines, such as earthmoving machines, for monitoring the position and guiding the travel of the machines. A typical position monitoring system includes a GPS (global positioning system) receiver located on-board a mobile machine to receive position data from a plurality of GPS satellites. In some circumstances, for example, when the machine is traveling within a tunnel, GPS signals may become unavailable. In such circumstances, an inertial navigation system may be employed to supplement the GPS system and to provide position data for the mobile machine. Such an inertial navigation system typically includes various inertial sensors, such as speed sensors, acceleration sensors, gyroscopes, etc.
A navigation apparatus is described in U.S. Patent Application Publication No. 2008/0109166 A1 (the '166 publication) to Takaoka et al. published on May 8, 2008. The navigation apparatus of the '166 publication includes a GPS processing section which receives and processes GPS signals, and an acceleration sensor. When the GPS signals become unavailable, position data is calculated based on acceleration signals provided by the acceleration sensor, and learning results provided by a learning section of an arithmetic processing unit which learns various parameters from previously received GPS signals before the GPS signals become unavailable.
Although the navigation apparatus of the '166 publication may provide autonomous position data when GPS signals become unavailable, the navigation apparatus may be problematic. For example, at least one of the GPS processing section and the acceleration sensor may malfunction and provide faulty position data, and the navigation apparatus of the '166 publication may not have the capacity to diagnose and detect such a malfunction.
The present disclosure is directed toward improvements in the existing technology.